miR-449a disturbs atherosclerotic plaque stability in streptozotocin and high-fat diet-induced diabetic mice by targeting CEACAM1

BACKGROUND

Emerging evidence indicates carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is involved in the development of atherosclerosis (AS). However, the roles and functions of CEACAM1 in AS remain unknown. Therefore, this study aims to investigate the roles and molecular functions of CEACAM1 in AS.

METHODS

We constructed a diabetes mellitus (DM) + high-fat diet (HFD) mouse model based on the streptozotocin (STZ)-induced apolipoprotein E-knockdown (ApopE-/-) mouse to investigate the roles and regulatory mechanism of miR-449a/CEACAM1 axis. The mRNA expression and protein levels in this study were examined using quantity PCR, western blot, immunofluorescence (IF), enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry (IHC), respectively. And the lipid deposition and collagen content were detected using Oil Red O and Sirius Red staining. Cell apoptosis, migration, invasion, and tuber formation were detected by Annexin-V FITC/PI, wound healing, transwell, and tuber formation assays, respectively. The relationship between miR-449a and CEACAM1 was determined by a dual-luciferase reporter gene assay.

RESULTS

miR-449a and MMP-9 were upregulated, and CEACAM1 was downregulated in the DM + HFD MOUSE model. Upregulation of CEACAM1 promoted atherosclerotic plaque stability and inhibited inflammation in the DM + HFD mouse model. And miR-449a directly targeted CEACAM1. Besides, miR-449a interacted with CEACAM1 to regulate atherosclerotic plaque stability and inflammation in DM-associated AS mice. In vitro, the rescue experiments showed miR-449a interacted with CEACAM1 to affect apoptosis, migration, invasion, and tuber formation ability in high glucose (HG)-induced HUVECs.

CONCLUSION

These results demonstrated that miR-449a promoted plaque instability and inflammation in DM and HFD-induced mice by targeting CEACAM1.

Update on cardiac imaging: A critical analysis

Imaging is instrumental in diagnosing and directing the management of atherosclerosis. In 1958 the first diagnostic coronary angiography (CA) was performed, and since then further development has led to new methods such as coronary CT angiography (CTA), optical coherence tomography (OCT), positron tomography (PET), and intravascular ultrasound (IVUS). Currently, CA remains powerful for visualizing coronary arteries; however, recent studies show the benefits of using other non-invasive techniques. This review identifies optimum imaging techniques for diagnosing and monitoring plaque stability. This becomes even direr now, given the rapidly rising incidence of atherosclerosis in society today. Many acute coronary events, including acute myocardial infarctions and sudden deaths, are attributable to plaque rupture. Although fatal, these events can be preventable. We discuss the factors affecting plaque integrity, such as increased inflammation, medications like statins, and increased lipid content. Some of these precipitating factors are identifiable through imaging. However, we also highlight significant complications arising in some modalities; in CA this can include ventricular arrhythmia and even death. Extending this, we elucidated from the literature that risk can also vary based on the location of arteries and their plaques. Promisingly, there are less invasive methods being trialled for assessing plaque stability, such as Cardiac Magnetic Resonance Imaging (CMR), which is already in use for other cardiac diseases like cardiomyopathies. Therefore, future research focusing on using imaging modalities in conjunction may be sensible, to bridge between the effectiveness of modalities, at the expense of increased complications, and vice versa.

Efficacy and potential mechanism of atherosclerosis prevention by the active components of leech based on network pharmacology combined with animal experiments

Introduction

Leeches are flesh-eating and bloodsucking parasitic worms. They are being used as a traditional Chinese medicine for centuries in activating blood and dissolving statis, dreging the meridims and tick. Hirudin, an active peptide product present in leech, has blood anticoagulant property and can assist in the treatment of thrombosis and diseases related to blood circulation. The efficacy and potential mechanism of action of leeches in such diseases should be further explored.

Materials and methods

First, network pharmacology was used to screen the predicted potential targets of the active constituents of leech and AS. The common targets of the active constituents of leech and AS were obtained using Venn diagram. Further, the drug-active-constituent-target network diagram, protein-protein interaction, and GO and KEGG pathway enrichment analyses were used to construct the active-constituent-AS target-pathway network diagram. Subsequently, the protein-drug molecule docking model was drawn. Finally, the results of network pharmacology were validated using a mouse model of AS.

Results

In total, 34 active constituents of leech and 1172 AS-related gene targets were selected, took the drug action targets and potential disease targets to get the common targets, and took the top 10 of degree value as the main active constituents for the treatment of atherosclerosis. There were 89 common targets and 12 core targets. The main targets included MAPK, EGFR, PIK3CB, etc. Potential regulatory pathways included cancer pathways, EGFR tyrosine kinase inhibitor resistance, Rap1 signaling pathway, PPAR signaling pathway, PI3K-Akt signaling pathway, C-type lectin receptor signaling pathway, and AGE-RAGE signaling pathway in diabetic complications. Animal experiments using mouse model of AS confirmed that AS plaques were smaller after treatment with leeches. SRC level was measured using western blotting. Expression of SRC in myocardial tissue was remarkably lower in the mice treated with leech than in the mice from model group fed on high-fat chow.

Conclusions

To the best of our knowledge, this is the first study to explore the mechanism of action of the active components of leech in AS prevention. The active components of leeches play a coordinated role in preventing AS through multicomponent, multitarget, and multichannel mechanism of action related to inflammatory response, oxidative stress, and lipid metabolism. This study provided a reference for subsequent cellular and animal experiments.

Suppression of endoplasmic reticulum stress by 4-PBA enhanced atherosclerotic plaque stability via up-regulating CLOCK expression

Endoplasmic reticulum (ER) stress refers to a condition where the normal functioning of the ER is disrupted due to a variety of cellular stress factors. As a result, there is an accumulation of unfolded and misfolded proteins within the ER. Numerous studies have shown that ER stress can exacerbate inflammatory reactions and contribute to the development of various inflammatory diseases. However, the role of ER stress in the stability of atherosclerotic plaques remains poorly understood. In this study, we aimed to explore the potential impact of a specific ER stress inhibitor known as 4-phenyl butyric acid (4-PBA) on atherosclerosis in mice. The mice were fed a high-fat diet, and treatment with 4-PBA significantly improved the stability of the atherosclerotic plaques. This was evidenced by a reduction in oxidative stress and an increase in circadian locomotor output cycles kaput (CLOCK) protein and mRNA expression within the plaques. Additionally, 4-PBA reduced the expression of ER stress-related proteins and decreased apoptosis in the atherosclerotic plaques. In vitro investigation, we observed the effect of 4-PBA on vascular smooth muscle cells (VSMCs) that were exposed to oxidized low-density lipoprotein (ox-LDL), a significant contributor to the development of atherosclerosis. 4-PBA reduced reactive oxygen species (ROS) production and attenuated apoptosis, GRP78 and CHOP protein expression in ox-LDL-Induced VSMCs via up-regulating CLOCK expression. However, when the short hairpin RNA against CLOCK (sh-CLOCK) was introduced to the VSMCs, the protective effect of 4-PBA was abolished. This suggests that the up-regulation of CLOCK expression is crucial for the beneficial effects of 4-PBA on atherosclerotic plaque stability. This finding suggests that targeting ER stress and modulating CLOCK protein levels might be a promising way to enhance the stability of atherosclerotic plaques.

Protocatechuic aldehyde increases pericyte coverage and mitigates pericyte damage to enhance the atherosclerotic plaque stability

Pericyte dysfunction and loss contribute substantially to the destabilization and rupture of atherosclerotic plaques. Protocatechuic aldehyde (PCAD), a natural polyphenol, exerts anti-atherosclerotic effects. However, the effects and mechanisms of this polyphenol on pericyte recruitment, coverage, and pericyte function remain unknown. We here treated apolipoprotein E-deficient mice having high-fat diet-induced atherosclerosis with PCAD. PCAD achieved therapeutic effects similar to rosuvastatin in lowering lipid levels and thus preventing atherosclerosis progression. With PCAD administration, plaque phenotype exhibited higher stability with markedly reduced lesion vulnerability, which is characterized by reduced lipid content and macrophage accumulation, and a consequent increase in collagen deposition. PCAD therapy increased pericyte coverage in the plaques, reduced VEGF-A production, and inhibited intraplaque neovascularization. PCAD promoted pericyte proliferation, adhesion, and migration to mitigate ox-LDL-induced pericyte dysfunction, which thus maintained the capillary network structure and stability. Furthermore, TGFBR1 silencing partially reversed the protective effect exerted by PCAD on human microvascular pericytes. PCAD increased pericyte coverage and impeded ox-LDL-induced damages through TGF-β1/TGFBR1/Smad2/3 signaling. All these novel findings indicated that PCAD increases pericyte coverage and alleviates pericyte damage to improve the stability of atherosclerotic plaques, which is accomplished by regulating TGF-β1/TGFBR1/Smad2/3 signaling in pericytes.

Haemodynamic Effects on the Development and Stability of Atherosclerotic Plaques in Arterial Blood Vessel

Studying the formation and stability of atherosclerotic plaques in the hemodynamic field is essential for understanding the growth mechanism and preventive treatment of atherosclerotic plaques. In this paper, based on a multiplayer porous wall model, we established a two-way fluid-solid interaction with time-varying inlet flow. The lipid-rich necrotic core (LRNC) and stress in atherosclerotic plaque were described for analyzing the stability of atherosclerotic plaques during the plaque growth by solving advection-diffusion-reaction equations with finite-element method. It was found that LRNC appeared when the lipid levels of apoptotic materials (such as macrophages, foam cells) in the plaque reached a specified lower concentration, and increased with the plaque growth. LRNC was positively correlated with the blood pressure and was negatively correlated with the blood flow velocity. The maximum stress was mainly located at the necrotic core and gradually moved toward the left shoulder of the plaque with the plaque growth, which increases the plaque instability and the risk of the plaque shedding. The computational model may contribute to understanding the mechanisms of early atherosclerotic plaque growth and the risk of instability in the plaque growth.

High dietary inflammatory index is associated with decreased plaque stability in patients with coronary heart disease

Coronary plaque stability is a key pathological mechanism of coronary heart disease (CHD). Inflammation is recognized as a key factor of coronary plaque stability. The dietary inflammatory index (DII) is calculated from 21 dietary nutrients to predict the inflammation potential of an individual's diet. We hypothesized that high DII may be associated with decreased coronary plaque stability in CHD patients; therefore, this study aimed to evaluate the association between DII and plaque stability in patients with CHD. This cross-sectional study included 314 patients with CHD. DII was calculated based on food frequency questionnaires. Plaque stability was measured with optical coherence tomography. The DII ranged from -1.41 to 3.04. After adjusting for confounding factors, higher DII scores were associated with unstable plaque characteristics including thin-capped fibroatheroma (odds ratio [OR], 3.60; 95% confidence interval [CI], 1.78-7.29), macrophage infiltration (OR, 2.16; 95% CI, 1.01-4.61), and plaque rupture (OR, 3.55; 95% CI, 1.73-7.29). Mediation analyses revealed that DII was important mediator of the relationship between plaque stability and food intake including soybeans and nuts, fish and shrimp, eggs (P < .05). The present study confirmed that higher DII is significantly associated with decreased plaque stability in CHD patients, suggesting an important protective role of anti-inflammatory diets in the pathogenesis of CHD.

Transforming growth factor-β2 is associated with atherosclerotic plaque stability and lower risk for cardiovascular events

AIMS

Transforming growth factor-beta (TGF-β) exists in three isoforms TGF-β1, -β2, and -β3. TGF-β1 has been suggested to be important for maintaining plaque stability, yet the role of TGF-β2 and -β3 in atherosclerosis remains to be investigated.This study explores the association of the three isoforms of TGF-β with plaque stability in the human atherosclerotic disease.

METHODS AND RESULTS

TGF-β1, -β2, and -β3 proteins were quantified in 223 human carotid plaques by immunoassays. Indications for the endarterectomy were: symptomatic carotid plaque with stenosis >70% or without symptoms and >80% stenosis. Plaque mRNA levels were assessed by RNA sequencing. Plaque components and extracellular matrix were measured histologically and biochemically. Matrix metalloproteinases and monocyte chemoattractant protein-1 (MCP-1) was measured with immunoassays. The effect of TGF-β2 on inflammation and protease activity was investigated in vitro using THP-1 and RAW264.7 macrophages. Patients were followed longitudinally for cardiovascular (CV) events.TGF-β2 was the most abundant isoform and was increased at both protein and mRNA levels in asymptomatic plaques. TGF-β2 was the main determinant separating asymptomatic plaques in an Orthogonal Projections to Latent Structures Discriminant Analysis. TGF-β2 correlated positively to features of plaque stability and inversely to markers of plaque vulnerability. TGF-β2 was the only isoform inversely correlated to the matrix-degrading matrix metalloproteinase-9 and inflammation in the plaque tissue. In vitro, TGF-β2 pre-treatment reduced MCP-1 gene and protein levels as well as matrix metalloproteinase-9 gene levels and activity. Patients with plaques with high TGF-β2 levels had a lower risk to suffer from future CV events.

CONCLUSIONS

TGF-β2 is the most abundant TGF-β isoform in human plaques and may maintain plaque stability by decreasing inflammation and matrix degradation.

Interleukin-6 trans-signaling induced laminin switch contributes to reduced trans-endothelial migration of granulocytic cells

BACKGROUND AND AIMS

Laminins are essential components of the endothelial basement membrane, which predominantly contains LN421 and LN521 isoforms. Regulation of laminin expression under pathophysiological conditions is largely unknown. In this study, we aimed to investigate the role of IL-6 in regulating endothelial laminin profile and characterize the impact of altered laminin composition on the phenotype, inflammatory response, and function of endothelial cells (ECs).

METHODS

HUVECs and HAECs were used for in vitro experiments. Trans-well migration experiments were performed using leukocytes isolated from peripheral blood of healthy donors. The BiKE cohort was used to assess expression of laminins in atherosclerotic plaques and healthy vessels. Gene and protein expression was analyzed using Microarray/qPCR and proximity extension assay, ELISA, immunostaining or immunoblotting techniques, respectively.

RESULTS

Stimulation of ECs with IL-6+sIL-6R, but not IL-6 alone, reduces expression of laminin α4 (LAMA4) and increases laminin α5 (LAMA5) expression at the mRNA and protein levels. In addition, IL-6+sIL-6R stimulation of ECs differentially regulates the release of several proteins including CXCL8 and CXCL10, which collectively were predicted to inhibit granulocyte transmigration. Experimentally, we demonstrated that granulocyte migration is inhibited across ECs pre-treated with IL-6+sIL-6R. In addition, granulocyte migration across ECs cultured on LN521 was significantly lower compared to LN421. In human atherosclerotic plaques, expression of endothelial LAMA4 and LAMA5 is significantly lower compared to control vessels. Moreover, LAMA5-to-LAMA4 expression ratio was negatively correlated with granulocytic cell markers (CD177 and myeloperoxidase (MPO)) and positively correlated with T-lymphocyte marker CD3.

CONCLUSIONS

We showed that expression of endothelial laminin alpha chains is regulated by IL-6 trans-signaling and contributes to inhibition of trans-endothelial migration of granulocytic cells. Further, expression of laminin alpha chains is altered in human atherosclerotic plaques and is related to intra-plaque abundance of leukocyte subpopulations.

Activation of estrogen receptor α inhibits TLR4 signaling in macrophages and alleviates the instability of atherosclerotic plaques in the postmenopausal stage

Acute cardiovascular events increase significantly in postmenopausal women. The relationship between estrogen receptor (ER) and plaque stability in the postmenopausal stage remains to be elucidated. We aimed to explore whether ERα activation improves plaque instability in the postmenopausal stage. Here, we report that postmenopausal women showed increased macrophage activation and plaque instability with increased MCP-1, MMP9, TLR4, MYD88 and NF-κB p65 and decreased ERα and TIMP1 expression in the vascular endothelium. Moreover, ovariectomy in LDLR-/- mice resulted in a significant increase in plaque area and necrotic core area, as well as a significant decrease in collagen content and an increase in macrophage accumulation in the artery. Ovariectomy also reduced serum estrogen levels and ERα expression and upregulated TLR4 and MMP9 expression in arteries in LDLR-/- mice. Estrogen or phytoestrogen therapy upregulated the expression level of ERα in ovariectomized mice and increased plaque stability by inhibiting macrophage accumulation and TLR4 signaling. In vitro, LPS incubation of RAW264.7 cells resulted in a significant decrease in ERα and TIMP1 expression and an increase in TLR4 activation, and estrogen or phytoestrogen treatment increased ERα and TIMP1 expression and inhibited TLR4 activation and MMP9 expression in LPS-treated RAW264.7 cells. Compared to control siRNA transfected RAW264.7 cells, TLR4 siRNA promoted TIMP1 expression in RAW264.7 cells with LPS incubation, but did not affect ERα expression in RAW264.7 cells with or without LPS treatment. The ERα inhibitor MPP abolished the regulatory effect of estrogen or phytoestrogen on LPS-induced RAW264.7 cells. In conclusion, the present study demonstrates that decreased ERα expression promotes macrophage infiltration and plaque instability in the postmenopausal stage, and activation of ERα in the postmenopausal stage alleviates atherosclerotic plaque instability by inhibiting TLR4 signaling and macrophage-related inflammation.

Atherosclerosis risk classification with computed tomography angiography: A radiologic-pathologic validation study

BACKGROUND AND AIMS

The application of machine learning to assess plaque risk phenotypes on cardiovascular CT angiography (CTA) is an area of active investigation. Studies using accepted histologic definitions of plaque risk as ground truth for machine learning models are uncommon. The aim was to evaluate the accuracy of a machine-learning software for determining plaque risk phenotype as compared to expert pathologists (histologic ground truth).

METHODS

Sections of atherosclerotic plaques paired with CTA were prospectively collected from patients undergoing carotid endarterectomy at two centers. Specimens were annotated for lipid-rich necrotic core, calcification, matrix, and intraplaque hemorrhage at 2 mm spacing and classified as minimal disease, stable plaque, or unstable plaque according to a modified American Heart Association histological definition. Phenotype is determined in two steps: plaque morphology is delineated according to histological tissue definitions, followed by a machine learning classifier. The performance in derivation and validation cohorts for plaque risk categorization and stenosis was compared to histologic ground truth at each matched cross-section.

RESULTS

A total of 496 and 408 vessel cross-sections in the derivation and validation cohorts (from 30 and 23 patients, respectively). The software demonstrated excellent agreement in the validation cohort with histological ground truth plaque risk phenotypes with weighted kappa of 0.82 [0.78-0.86] and area under the receiver operating curve for correct identification of plaque type was 0.97 [0.96, 0.98], 0.95 [0.94, 0.97], 0.99 [0.99, 1.0] for unstable plaque, stable plaque, and minimal disease, respectively. Diameter stenosis correlated poorly to histologically defined plaque type; weighted kappa 0.25 in the validation cohort.

CONCLUSIONS

A machine-learning software trained on histological ground-truth tissue inputs demonstrated high accuracy for identifying plaque stability phenotypes as compared to expert pathologists.

Qing-Xin-Jie-Yu Granule inhibits ferroptosis and stabilizes atherosclerotic plaques by regulating the GPX4/xCT signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Qing-Xin-Jie-Yu Granule (QXJYG) is an integrated traditional Chinese medicine formula used to treat atherosclerotic (AS) cardiovascular diseases. A randomized controlled trial found that QXJYG reduced cardiovascular events and experiments also verified that QXJYG attenuated AS by remodeling the intestinal flora.

AIM OF THE STUDY

To determine whether QXJYG would attenuate AS and plaque vulnerability by regulating ferroptosis in high-fat diet-induced atherosclerotic ApoE-/- mice and to investigate the effects of QXJYG on macrophage ferroptosis in RAS-selective lethal 3 (RSL3)-induced J744A.1 cells.

METHODS

AS models in ApoE-/- mice and RSL3-induced ferroptosis in J744A.1 cells were established to measure the protective and anti-ferroptotic effects of QXJYG in vivo and in vitro. The glutathione peroxidase 4 (GPX4)/cystine glutamate reverse transporter (xCT) signal pathway was examined by immunohistochemistry and western blotting.

RESULTS

QXJYG attenuated AS progression and plaque vulnerability. Characteristic morphological changes of ferroptosis in the QXJYG-treated animals were rare. Total iron was significantly lower in the QXJYG group than in the model group (P < 0.05); QXJYG suppressed the lipid peroxidation (LPO) levels (malondialdehyde), enhanced the antioxidant capacity (superoxide dismutase and glutathione), and reduced inflammatory factors (interleukin [IL]-6, IL-1β, tumor necrosis factor-α) associated with ferroptosis. Expression of GPX4/xCT in aorta tissues was remarkably increased in the QXJYG group. QXJYG inhibited ferroptosis in J744A.1 macrophages disturbed using RSL3. The Fe2+, LPO, and reactive oxygen species levels were lower in the QXJYG group than in the RSL3 group (P < 0.05). The QXJYG group showed higher expression of the GPX4/xCT signal pathway.

CONCLUSION

QXJYG inhibits ferroptosis in vulnerable AS plaques partially via the GPX4/xCT signaling pathway.

The Correlation between Increased Expressions of NLRP3 Inflammasome Components in Peripheral Blood Mono-Nuclear Cells and Plaque Vulnerability in Human Carotid Atherosclerosis

Background

We aimed to determine whether NLRP3 inflammasomes in peripheral blood mononuclear cells (PBMC) were associated with carotid plaque instability in carotid atherosclerosis patients.

Methods

Consecutive 38 carotid atherosclerosis with vulnerable plaques, 22 carotid atherosclerosis with stable plaques, and 40 healthy subjects with no carotid or coronary artery stenosis were enrolled. They were referred to the Second Hospital of Dalian Medical University from 2013-2019. Carotid plaques were evaluated by modified plaque vulnerability risk score (MPVRS) and pathological assessment. The mRNA and protein expression of NLRP3 inflammasome components in PBMC were determined by quantitative real time PCR and Western blot analysis or ELISA.

Results

When consecutive study subjects undergoing carotid endarterectomy were divided into stable (≤4) and unstable (>4) plaque groups according to the MPVRS, the unstable plaque group had significantly raised mRNA and protein expression of NLRP3 inflammasome components in PBMC as compared with the stable plaque group and healthy subject group. Furthermore, subjects with higher NLRP3 protein expression in PBMC had greater incidence of cerebrovascular events.

Conclusion

Increased NLRP3 inflammasome components in PBMC is associated with instability of human carotid atherosclerotic plaques, suggesting NLRP3 inflammasome as a potential biomarker for monitoring carotid plaque instability.

Role of Sp1 in atherosclerosis

Specificity protein (Sp) is a famous family of transcription factors including Sp1, Sp2 and Sp3. Sp1 is the first one of Sp family proteins to be characterized and cloned in mammalian. It has been proposed that Sp1 acts as a modulator of the expression of target gene through interacting with a series of proteins, especially with transcriptional factors, and thereby contributes to the regulation of diverse biological processes. Notably, growing evidence indicates that Sp1 is involved in the main events in the development of atherosclerosis (AS), such as inflammation, lipid metabolism, plaque stability, vascular smooth muscle cells (VSMCs) proliferation and endothelial dysfunction. This review is designed to provide useful clues to further understanding roles of Sp1 in the pathogenesis of AS, and may be helpful for the design of novel efficacious therapeutics agents targeting Sp1.

BMAL1 modulates smooth muscle cells phenotypic switch towards fibroblast-like cells and stabilizes atherosclerotic plaques by upregulating YAP1

BACKGROUND

Ischemic heart diseases and ischemic stroke are closely related to circadian clock and unstable atherosclerotic plaques. Vascular smooth muscle cells (VSMCs) can stabilize or destabilize an atherosclerotic lesion through phenotypic switch. BMAL1 is not only an indispensable core component in circadian clock but also an important regulator in atherosclerosis and VSMCs proliferation. However, little is known about the modulation mechanisms of BMAL1 in VSMCs phenotypic switch and atherosclerotic plaque stability.

METHODS

We integrated histological analysis of human plaques, in vivo experiments of VSMC-specific Bmal1-/- mice, in vitro experiments, and gene set enrichment analysis (GSEA) of public datasets of human plaques to explore the function of BMAL1 in VSMCs phonotypic switch and plaque stability.

FINDINGS

Comparing to human unstable plaques, BMAL1 was higher in stable plaques, accompanied by elevated YAP1 and fibroblast maker FSP1 which were positively correlated with BMAL1. In response to Methyl-β-cyclodextrin-cholesterol, oxidized-low-density-lipoprotein and platelet-derived-growth-factor-BB, VSMCs embarked on phenotypic switch and upregulated BMAL, YAP1 and FSP1. Besides, BMAL1 overexpression promoted VSMCs phonotypic switch towards fibroblast-like cells by transcriptionally upregulating the expression of YAP1. BMAL1 or YAP1 knock-down inhibited VSMCs phonotypic switch and downregulated FSP1. Furthermore, VSMC-specific Bmal1-/- mice exhibited VSMCs with lower YAP1 and FSP1 levels, and more vulnerable plaques with less collagen content. In addition, BMAL1 suppressed the migration of VSMCs. The GSEA results of public datasets were consistent with our laboratory findings.

INTERPRETATION

Our results highlight the importance of BMAL1 as a major regulator in VSMCs phenotypic switch towards fibroblast-like cells which stabilize an atherosclerotic plaque.

Exercise training inhibits atherosclerosis progression and reduces VE-cadherin levels within atherosclerotic plaques in hypercholesterolemic mice

Vascular endothelial-cadherin (VE-cadherin), matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) have emerged as key-factors of atherogenesis. The aim of this study was to evaluate the effects of exercise training (ET) on those key-factors in relation to the progression of atherosclerotic lesions in hypercholesterolemic mice. Thirty male, apoE knockout (apoE^-/-) mice were randomly assigned to the following equivalent groups: 1) CO-control: High-fat diet (HFD) administration for 12 weeks. 2) EX-exercise: HFD administration as in CO, and during the last 4 weeks (9th -12th week) ET on treadmill (5sessions/week, 60min/session). At the end of study, blood samples were obtained and all mice were sacrificed. Aortic roots were excised and analysed regarding the percentage of aortic stenosis, and the relative concentrations of collagen, elastin, VE-cadherin, MMP-8,-9 and TIMP-1,-2 within the atherosclerotic lesions. Aortic stenosis was significantly lower in the EX than the CO group (39.63 ± 7.22% vs 62.04 ± 8.55%; p < 0.001), along with considerable increase in fibrous cap thickness and of collagen and elastin contents within plaques (p < 0.05). Compared to controls, exercised-treated mice showed reduced intra-plaque relative concentrations of VE-cadherin (15.09 ± 1.89% vs 23.49 ± 3.01%, p < 0.001), MMP-8 (8.51 ± 2.24% vs 18.51 ± 4.08%, p < 0.001) and MMP-9 (12.1 ± 4.86% vs 18.88 ± 6.23%, p < 0.001). Inversely, the relative concentrations of TIMP-1 and TIMP-2 in the ET group were considerably higher by 62.5% and 31.2% than in the EX group (p < 0.05), respectively. Finally, body weight and lipids concentrations did not differ between groups at the end of the study (p > 0.05). ET treatment induced regression of established atherosclerotic lesions in apoE^-/- mice and improved their stability. Those effects seemed to be mediated by favourable modification of VE-cadherin, MMPs and TIMPs.

miR-146a contributes to atherosclerotic plaque stability by regulating the expression of TRAF6 and IRAK-1

BACKGROUND

Atherosclerosis is a chronic inflammatory disease. The vulnerable plaque of atherosclerotic can lead to the development of many diseases including acute coronary syndrome and coronary heart disease. It is well known that miR-146a is the key brake miRNA of the inflammatory signal transduction pathway. However, the effect of miR-146a on the stability of atherosclerotic plaque remains to be elucidated.

METHODS AND RESULTS

We constructed animal models of atherosclerosis and foam cell models, and overexpressed and knocked-down miR-146a in models. After staining with Hematoxylin-Eosin (HE), Oil Red O, immunocytochemistry (IHC) and Sirius Red, we used the proportion of (Lipids area + Macrophage area) and (SMCs area + collagen area) to evaluate atherosclerotic plaque stability. TUNEL and flow cytometry were performed to detect the apoptosis level of macrophages. Levels of inflammatory factors were detected via ELISA assay. The results showed that miR-146a, IRAK1 and TRAF6 were abnormally expressed in plaques of atherosclerotic animals. Overexpression of miR-146a contributed to the stability of plaques that inhibited plaque formation, macrophage apoptosis and levels of pro-inflammatory factors. The Dual-luciferase reporter gene assay, IF and FISH were used to verify the regulatory mechanism of miR-146a on IRAK1 and TRAF6. We found that IRAK1 and TRAF6 promoted lipid uptake, apoptosis, and release of pro-inflammatory factors of RAW264.7 macrophages, whereas miR-146a restored RAW264.7 macrophages phenotype by inhibiting IRAK1 and TRAF6 expression.

CONCLUSIONS

We display for the first time that miR-146a inhibits the formation of foam cells, RAW264.7 macrophage apoptosis and pro-inflammatory reaction through negative regulation of IRAK1 and TRAF6 expression, thereby enhancing the stability of atherosclerotic plaques.

Research on the correlation between activating transcription factor 3 expression in the human coronary artery and atherosclerotic plaque stability

Background

Activating transcription factor 3 (ATF3) is an early response gene that is activated in response to atherosclerotic stimulation and may be an important factor in inhibiting the progression of atherosclerosis. In this study, we directly measured the expression of ATF3 and inflammatory factors in human coronary atherosclerotic plaques to examine the relationship between ATF3 expression, inflammation and structural stability in human coronary atherosclerotic plaques.

Methods

A total of 68 coronary artery specimens were collected from the autopsy group, including 36 cases of sudden death from coronary heart disease (SCD group) and 32 cases of acute death caused by mechanical injury with coronary atherosclerosis (CHD group). Twenty-two patients who had no coronary heart disease were collected as the control group (Con group). The histological structure of the coronary artery was observed under a light microscope after routine HE staining, and the intimal and lesion thicknesses, thickness of the fibrous cap, thickness of necrosis core, degree of lumen stenosis were assessed by image analysis software. Western blotting and immunohistochemistry were used to measure the expression and distribution of ATF3, inflammatory factors (CD45, IL-1β, TNF-α) and matrix metalloproteinase-9 (MMP-9) and vascular cell adhesion molecule 1 (VCAM1) in the coronary artery. The Pearson correlation coefficient was used to analyse the correlation between ATF3 protein expression and inflammatory factors and between ATF3 protein expression and structure-related indexes in the lesion group.

Results

Compared with those in the control group, the intima and necrotic core in the coronary artery were thickened, the fibrous cap became thin and the degree of vascular stenosis was increased in the lesion group, while the intima and necrotic core became thicker and the fibrous cap became thinner in the SCD group than in the CHD group (P < 0.05). There was no or low expression of ATF3, inflammatory factors, VCAM1 and MMP-9 in the control group, and the expression of inflammatory factors, VCAM1 and MMP-9 in the SCD group was higher than that in CHD group, while the expression of ATF3 in the SCD group was significantly lower than that in CHD group (P < 0.05). In the lesion group, the expression of ATF3 was negatively correlated with intimal and necrotic focus thickness, positively correlated with fibrous cap thickness (P < 0.01), and negatively correlated with inflammatory factors, VCAM1 and MMP-9 (P < 0.01).

Conclusions

The expression of ATF3 may be related to the progression and stability of atherosclerotic plaques, and may affect the structural stability of atherosclerotic plaques by regulating the inflammatory response, thus participating in the regulation of atherosclerotic progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02161-9.

Circadian misalignment promotes vascular smooth muscle cell apoptosis via defective autophagy

Defective autophagy in vascular smooth muscle cells (VSMCs) in response to oxidative stress can lead to cellular apoptosis and plaque instability. Previous studies have revealed that the circadian clock system is involved in autophagic regulation and plaque progression. However, the mechanism by which circadian rhythmicity influences VSMC autophagy and plaque stability remains unclear. Our study described the circadian profiles in atheromatous plaques and verified the role of circadian misalignment in VSMC autophagy and apoptosis. We found that the mRNA expression levels of circadian locomotor output cycles protein kaput (CLOCK) and Beclin 1 were significantly decreased in unstable plaques compared with stable plaques. No significant differences were observed in other circadian rhythm genes. VSMCs treated with oxidized low-density lipoprotein (ox-LDL, 80 μg/ml) exhibited abnormal circadian rhythmicity and impaired autophagy, as evidenced by consistent decreases in CLOCK and Beclin 1 expression, suggesting a correlation between CLOCK and autophagy. CLOCK protein expression was inhibited by ox-LDL, accompanied by defective autophagy and an increased apoptosis rates (P < 0.05). Administration of rapamycin (10 nM) reversed the effect of ox-LDL on VSMC autophagy and apoptosis. Finally, CLOCK silencing led to a considerable decrease in autophagy. VSMCs with stable CLOCK silencing also showed an increased apoptosis rate. In addition, gene silencing of CLOCK in VSMCs counteracted the effects of moderate rapamycin concentrations on autophagy and apoptosis. In conclusion, these findings suggested that the CLOCK-dependent rapamycin signaling pathway is a critical mediator in ox-LDL-induced VSMCs with defective autophagy that exacerbates plaque destabilization.

7-Difluoromethoxy-5,4'-dimethoxy-genistein attenuates macrophages apoptosis to promote plaque stability via TIPE2/TLR4 axis in high fat diet-fed ApoE-/- mice

Promoting plaque stability is of great significance for prevention and treatment of cardiovascular diseases. 7-difluoromethoxy-5,4'-dimethoxygenistein (DFMG) is a novel active compound synthesized using genistein, which exerts anti-atherosclerotic effect. In this study, we evaluated effects of DFMG on plaque stability in ApoE^-/- mice fed with high fat diet (HFD), and explored the molecular mechanism by using ApoE^-/-TLR4^-/- mice and RAW264.7 cells. Here, we found that DFMG significantly reduced plaque areas, macrophages infiltration and apoptosis, and TLR4 expression in HFD-fed ApoE^-/- mice. Meanwhile, DFMG increased collagen fibers, smooth muscle cells and TIPE2 expression in plaques and media. Besides, TLR4 knockout promoted the protective effects of DFMG on plaques. In vitro, DFMG decreased lysophosphatidylcholine (LPC)-induced macrophages apoptosis and TLR4, while upregulated TIPE2. Moreover, TIPE2 reduced TLR4, MyD88, p-NF-κB p65^Ser276, cleaved Caspase-3 overproduction, and enhanced effects of DFMG on LPC-induced macrophages. Overall, our study demonstrates that DFMG can promote plaque stability by reducing macrophage apoptosis through TIPE2/TLR4 signaling pathway, which suggests DFMG should be used to develop food additives or drugs for preventing atherosclerosis.

Deletion of fibroblast activation protein provides atheroprotection

AIMS

Fibroblast activation protein (FAP) is upregulated at sites of tissue remodelling including chronic arthritis, solid tumours, and fibrotic hearts. It has also been associated with human coronary atherosclerotic plaques. Yet, the causal role of FAP in atherosclerosis remains unknown. To investigate the cause-effect relationship of endogenous FAP in atherogenesis, we assessed the effects of constitutive Fap deletion on plaque formation in atherosclerosis-prone apolipoprotein E (Apoe) or low-density lipoprotein receptor (Ldlr) knockout mice.

METHODS AND RESULTS

Using en face analyses of thoraco-abdominal aortae and aortic sinus cross-sections, we demonstrate that Fap deficiency decreased plaque formation in two atherosclerotic mouse models (-46% in Apoe and -34% in Ldlr knockout mice). As a surrogate of plaque vulnerability fibrous cap thickness was used; it was increased in Fap-deficient mice, whereas Sirius red staining demonstrated that total collagen content remained unchanged. Using polarized light, atherosclerotic lesions from Fap-deficient mice displayed increased FAP targets in terms of enhanced collagen birefringence in plaques and increased pre-COL3A1 expression in aortic lysates. Analyses of the Stockholm Atherosclerosis Gene Expression data revealed that FAP expression was increased in human atherosclerotic compared to non-atherosclerotic arteries.

CONCLUSIONS

Our data provide causal evidence that constitutive Fap deletion decreases progression of experimental atherosclerosis and increases features of plaque stability with decreased collagen breakdown. Thus, inhibition of FAP expression or activity may not only represent a promising therapeutic target in atherosclerosis but appears safe at the experimental level for FAP-targeted cancer therapies.

Calcium deposition within coronary atherosclerotic lesion: Implications for plaque stability

Atherosclerotic lesion progression is associated with intimal calcification. The earliest lesion that shows calcification is pathologic intimal thickening in which calcifications appear as microcalcifications that vary in size from <0.5 to 15 μm. The calcifications become larger as plaques progress, becoming punctate (>15 μm to 1 mm in diameter), fragmented (>1 mm), and eventually sheet-like calcification (>3 mm). When stratified by plaque type, maximum calcifications are observed in fibrocalcific plaques, followed by healed plaque ruptures. Lesions of acute thrombi, i.e., plaque rupture and erosions, which are the most frequent causes of acute coronary syndromes, show much less calcification than stable fibrocalcific plaques. Conversely, a calcified nodule, the least common lesion of acute thrombosis, occurs in highly calcified lesions. Pro-inflammatory cytokines observed in unstable plaques may provoke an early phase of osteogenic differentiation of smooth muscle cells (SMCs), a release of calcifying extracellular matrix vesicles, and/or induce apoptosis of macrophages and SMCs, which also calcify. Recent pathologic and imaging based studies indicate that lesions with dense calcifications are more likely to be stable plaques (fibrocalcific plaques), while micro, punctate, or fragmented calcifications are associated with either early stage plaques or unstable lesions (plaque rupture or erosion). Clinical non-invasive computed tomography (CT) studies show that the greater the calcium score, the higher the likelihood of patients developing future acute coronary events. This appears contradictory with the findings from pathologic autopsy studies. However, CT analysis of calcium subtypes is limited by resolution and blooming artifacts. Thus, areas of heavy calcification may not be the cause of future events as pathologic studies suggest. Rather, calcium may be an overall marker for the extent of disease. These types of discrepancies can perhaps be resolved by invasive or non-invasive high resolution imaging studies carried out at intervals in patients who present with acute coronary syndromes versus stable angina patients. Coronary calcium burden is greater in stable plaques than unstable plaques and there is a negative correlation between necrotic core area and area of calcification. Recent clinical studies have demonstrated that statins can reduce plaque burden by demonstrating a reduction in percent and total atheroma volume. However, calcification volume increases. In summary, pathologic studies show that sheet calcification is highly prevalent in stable plaques, while microcalcifications, punctate, and fragmented calcifications are more frequent in unstable lesions. Both pathologic and detailed analysis of imaging studies in living patients can resolve some of the controversies in our understanding of coronary calcification.

Oleoylethanolamide stabilizes atherosclerotic plaque through regulating macrophage polarization via AMPK-PPARα pathway

BACKGROUND

Atherosclerotic plaque rupture is the major trigger of acute cardiovascular risk events, and manipulation of M1/M2 macrophage homeostasis is an effective strategy for regulating atherosclerotic plaque stability. This study was aimed to illuminate the effects of oleoylethanolamide (OEA) on macrophage polarization and plaque stability.

METHODS

Macrophages derived from THP-1 were treated with OEA followed by LPS/IFN-γ, and the markers of M1, M2 macrophages were monitored by western blot, real-time PCR and immunofluorescence staining. The effect of OEA on macrophage polarization in the arch of aortic arteries was tested by immunofluorescence staining and western blot, and the plaque stability was completed by Masson's trichrome and hematoxylin and eosin (HE) in apolipoprotein E (ApoE)^-/- mice.

RESULTS

OEA treatment enhanced the expression of two classic M2 macrophage markers, macrophage mannose receptor (CD206) and transforming growth factor (TGF-β), while the expression of iNOS (M1 macrophages) was decreased in THP-1-derived macrophages. Blocking of PPARα using siRNA and inhibition of AMP-activated protein kinase (AMPK) by its inhibitor compound C attenuated the OEA-induced expression of M2 macrophage markers. In addition, OEA significantly suppressed M1, promoted M2 macrophage polarization, increased collagen content and decreased necrotic core size in atherosclerotic plaques in ApoE^-/- mice, which were linked with the expression of PPARα.

CONCLUSIONS

OEA improved atherosclerotic plaque stability through regulating macrophage polarization via AMPK-PPARα pathway.

The role of OX40L and ICAM-1 in the stability of coronary atherosclerotic plaques and their relationship with sudden coronary death

Background

Coronary heart disease is related to sudden death caused by multi-factors and a major threat to human health.This study explores the role of OX40L and ICAM-1 in the stability of coronary plaques and their relationship with sudden coronary death.

Methods

A total of 118 human coronary arteries with different degrees of atherosclerosis and/or sudden coronary death comprised the experimental group and 28 healthy subjects constituted the control group were isolated from patients. The experimental group was subdivided based on whether the cause of death was sudden coronary death and whether it was accompanied by thrombosis, plaque rupture, plaque outflow and other secondary changes: group I: patients with coronary atherosclerosis but not sudden coronary death, group II: sudden coronary death without any of the secondary changes mentioned above, group III: sudden coronary death with coronary artery atherosclerotic lesions accompanied by either of the above secondary changes. The histological structure of the coronary artery was observed under a light microscope after routine HE staining, and the related indexes of atherosclerotic plaque lesions were assessed by image analysis software. The expressions of OX40L and ICAM-1 were detected by real-time quantitative PCR (RT-PCR), immunohistochemistry (IHC) and Western blotting, and the correlations between the expressions and the stability of coronary atherosclerotic plaque and sudden coronary death were analyzed.

Results

(1) The expression of OX40L protein in the control group and the three experimental groups showed an increasing trend, and the difference between groups was statistically significant (P < 0.05). (2) The expression of the ICAM-1 protein in the control group and the three experimental groups showed a statistically significant (P < 0.05) increasing trend. (3) The expression of OX40L and ICAM-1 mRNAs increased in the control and the three experimental groups and the difference was statistically significant (P < 0.05).

Conclusion

The expression of OX40L and ICAM-1 proteins and mRNAs is positively correlated with the stability of coronary atherosclerotic plaque and sudden coronary death.

Inhibition of perivascular mast cell activation is involved in the atheroprotective effect of rosiglitazone in apolipoprotein E-deficient mice

Activation of perivascular mast cells (MCs) and subsequent release of their abundant inflammatory mediators have been well documented to induce excessive inflammation and subsequent rupture of atherosclerotic plaques. Previous studies have suggested that rosiglitazone affects the stability of plaques, although the precise mechanism of action is not clearly understood. In this study, we evaluated the effects of rosiglitazone on MCs in vivo and in vitro. Apolipoprotein E-deficient (ApoE^-/-) mice were fed a high-fat diet (HFD), with or without rosiglitazone supplemented in the drinking water (1.5 mg/kg/day). Compared with the HFD group, rosiglitazone did not affect blood glucose levels, but it attenuated serum levels of tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6), ameliorated plaque lipid accumulation and the expression of matrix metalloproteinases-2 and -9, increased the collagen content of plaques, and inhibited perivascular MC degranulation and chymase expression. The in vitro experiments showed that rosiglitazone treatment repressed the expression of TNFα and IL-6 induced by antigen-challenged RBL-2H3 cells in a peroxisome proliferator-activated receptor γ (PPARγ)-independent manner, which was related to the repression of protein kinase C (PKC)-β1 activation. Combined, these results suggest that the plaque-stabilizing effect of rosiglitazone is attributable to its ability to inhibit the activation of perivascular MCs.

IL-33/IL-33R in various types of carotid artery atherosclerotic lesions

OBJECTIVE

Inflammation plays a crucial role in the progression of atherosclerotic plaques. The aim of the study was to investigate serum levels and expression of Interleukin-33 (IL-33) and ST2 receptor in atherosclerotic plaques and to analyze correlation with the type of the carotid plaques in patients with carotid disease.

METHODS

This study included 191 consecutive patients submitted for carotid endarterectomy (CEA). Preoperative serum levels of IL-33 and soluble ST2 (sST2) were measured. Atherosclerotic plaques obtained during surgery were initially histologically classified and immunohistochemical analyzes of IL-33, IL-33R, CD68 and alpha-SMA expression was performed. Ultrasound assessment of the level of carotid stenosis in each patient was performed prior to carotid surgery. Demographic and clinical data such as gender, age, smoking status, blood pressure, glycaemia, hemoglobin and creatinine levels, and comorbidities were collected and the comparisons between variables were statistically evaluated.

RESULTS

Serum levels of IL-33 (35.86 ± 7.93 pg/ml vs.12.29 ± 1.8 pg/ml, p < 0.05) and sST2 (183 ± 8.03 pg/ml vs. 122.31 ± 15.89 pg/ml, p < 0.05) were significantly higher in the group of CEA patients vs. healthy subjects. We demonstrated abundant tissue expression of IL-33 and ST2 in atherosclerotic carotid artery lesions. The levels of IL-33 and IL-33R expression were significantly higher in vulnerable plaques and significantly correlated with the degree of inflammatory cells infiltration in these plaques (R = 0.579, p = 0.049). Immunohistochemical analysis also revealed that cells responsible for IL-33 expression are not only mononuclear cells confined to inflammatory atherosclerotic lesions, but also smooth muscle cells which gained phenotypic characteristics of foam cells and were loaded with lipid droplets.

CONCLUSION

The obtained results confirm the importance of IL-33/ST2 axis in the process of atherosclerosis, and indicate its ambiguous function in immune response, whether as proinflammatory cytokine in advanced atherosclerotic lesions, or as profibrotic, in early lesions.

Simultaneous evaluation of plaque stability and ischemic potential of coronary lesions in a fluid-structure interaction analysis

The measurement of fractional flow reserve (FFR) and superficial wall stress (SWS) identifies inducible myocardial ischemia and plaque vulnerability, respectively. A simultaneous evaluation of both FFR and SWS is still lacking, while it may have a major impact on therapy. A new computational model of one-way fluid-structure interaction (FSI) was implemented and used to perform a total of 54 analyses in virtual coronary lesion models, based on plaque compositions, arterial remodeling patterns, and stenosis morphologies under physiological conditions. Due to a greater lumen dilation and more induced strain, FFR in the lipid-rich lesions (0.81 ± 0.15) was higher than that in fibrous lesions (0.79 ± 0.16, P = 0.001) and calcified lesions (0.79 ± 0.16, P = 0.001). Four types of lesions were further defined, based on the combination of cutoff values for FFR (0.80) and maximum relative SWS (30 kPa): The level of risk increased from (1) plaques with mild-to-moderate stenosis but negative remodeling for lipid-rich (Type A: non-ischemic, stable) to (2) lipid-rich plaques with mild-to-moderate stenosis and without-to-positive remodeling (Type B: non-ischemic, unstable) or plaques with severe stenosis but negative remodeling for lipid-rich (Type C: ischemic, stable) to (3) lipid-rich plaques with severe stenosis and without-to-positive remodeling (Type D: ischemic, unstable). The analysis of FSI to simultaneously evaluate inducible myocardial ischemia and plaque stability may be useful to identify coronary lesions at a high risk and to ultimately optimize treatment. Further research is warranted to assess whether a more aggressive treatment may improve the prognosis of patients with non-ischemic, intermediate, and unstable lesions.

Hydrogen sulfide stabilizes atherosclerotic plaques in apolipoprotein E knockout mice

Hydrogen sulfide gas (H₂S) has protective effects in the cardiovascular system that includes preventing the development of atherosclerosis when tested in several in vivo models. Plaque instability is a major risk factor for thromboembolism, myocardial infarction, and stroke, so we examined if H₂S can promote plaque stability and the potential underlying mechanisms. Apolipoprotein E knockout mice fed an atherogenic diet were administered the exogenous H₂S donor sodium hydrosulfide (NaHS) or pravastatin as a positive control daily for 14 weeks. NaHS significantly enhanced plaque stability by increasing fibrous cap thickness and collagen content compared to vehicle-treated controls. NaHS treatment also reduced blood lipid levels and plaque formation. Preservation of plaque stability by NaHS was associated with reductions in vascular smooth muscle cells (VSMCs) apoptosis and expression of the collagen-degrading enzyme matrix metallopeptidase-9 (MMP-9) in plaque. While pravastatin also increased fibrous cap thickness and reduced VSMC apoptosis, but did not enhance plaque collagen or reduce MMP-9 significantly, suggesting distinct mechanisms of plaque stabilization. in vitro, NaHS also decreased MMP-9 expression in macrophages stimulated with tumor necrosis factor-α by inhibiting ERK/JNK phosphorylation and activator protein 1 nuclear translocation. Moreover, H₂S reduced caspase-3/9 activity, Bax/Bcl-2 ratio, and LOX-1 mRNA expression in VSMCs stimulated with oxidized low-density lipoprotein. These results suggest that H₂S enhances plaque stability and protects against atherogenesis by increasing plaque collagen content and VSMC count. In conclusion, H₂S exerts protective effects against atherogenesis at least partly by stabilizing atherosclerotic plaque.

Small HDL subclass is associated with coronary plaque stability: An optical coherence tomography study in patients with coronary artery disease

BACKGROUND

The role of high-density lipoprotein (HDL) subclasses in atherosclerotic diseases remains an open question. Previous clinical trials have attempted to explore the predictive effect of HDL subspecies on cardiovascular risk. However, no studies have assessed the connections between these subclasses and characteristics of plaque microstructure.

OBJECTIVE

To investigate the relationship of HDL subclasses and coronary plaque stability assessed by optical coherence tomography (OCT).

METHODS

Morphological characteristics of 160 nontarget lesions from 85 patients with coronary artery disease were assessed by OCT. HDL subclass profiles were analyzed using nondenaturing polyacrylamide gel electrophoresis.

RESULTS

The plasma levels of small HDL subclass (percentage or concentration) were found to be positively associated with fibrous cap thickness (r = 0.232, P = .007; r = 0.243, P = .005) and negatively with maximum lipid arc (r = -0.240, P = .005; r = -0.252, P = .003) and lipid core length (r = -0.350, P < .001; r = -0.367, P < .001). Multivariate logistic regression analysis showed the small HDL subclass (percentage or concentration) (odds ratio [OR]: 0.457, 95% confidence interval [CI]: 0.214-0.974, P = .043; OR: 0.438, 95% CI: 0.204-0.938, P = .034) to be an independent factor in predicting OCT-detected thin-cap fibroatheroma of nontarget lesions.

CONCLUSION

High levels of small HDL are associated with coronary nontarget plaque stability. Our findings suggest that the small HDL subtype might represent the atheroprotective activity of HDL.

Matrix Gla Protein, Plaque Stability, and Cardiovascular Events in Patients with Severe Atherosclerotic Disease

OBJECTIVE

This study aims to investigate whether plasma matrix Gla protein (MGP) species, desphospho-uncarboxylated (dp-uc) MGP, and total uncarboxylated (t-uc) MGP are associated with plaque levels of uncarboxylated (uc) MGP, markers of plaque stability, and cardiovascular disease (CVD) risk.

METHODS

From the Athero-Express biobank, we selected carotid plaque samples of 100 patients who underwent carotid endarterectomy. The level of agreement between plasma MGP species and plaque ucMGP levels was assessed using weighted kappa (κ). We analyzed histological characteristics of plaque composition (plaque hemorrhage, lipid and calcification content). Logistic regression analyses were used to assess the association between plasma MGP and plaque characteristics. Furthermore, CVD endpoints (n = 20) were collected over a mean follow-up of 2.6 years.

RESULTS

Weighted κ statistics of plasma dp-ucMGP and t-ucMGP and plaque ucMGP were 0.10 (95% CI -0.31 to 0.52) and 0.14 (95% CI -0.20 to 0.48). Higher dp-ucMGP levels tended to be associated with less plaque hemorrhage (ORper 500 nM 0.96; 95% CI 0.92-1.00). No association was found for lipid and calcification content. Cox proportional hazards models showed no association between dp-ucMGP (HRper 200 pM 0.92; 95% CI 0.75-1.11) and an inverse association between t-ucMGP (HRper 500 nM 0.79; 95% CI 0.62-0.99) and cardiovascular events.

CONCLUSIONS

Plasma dp-ucMGP and t-ucMGP concentrations do not reflect plaque ucMGP levels. Elevated dp-ucMGP levels may be associated with less plaque hemorrhage, suggestive of more stable plaques. T-ucMGP was not related with markers of plaque stability; however, elevated plasma t-ucMGP levels were associated with a reduced CVD risk.

Loss of CLOCK under high glucose upregulates ROCK1-mediated endothelial to mesenchymal transition and aggravates plaque vulnerability

BACKGROUND AND AIMS

Carotid atherosclerotic plaque is one of the main sources of ischemic stroke, and endothelial-to-mesenchymal transition (EndMT) is a major feature of atherosclerosis. Rho-associated coiled-coil-containing protein kinase 1 (ROCK1) activation, stimulated by high glucose, plays an important role in EndMT, and circadian locomotor output cycles protein kaput (Clock) deficiency leads to hyperglycemia and enhanced atherosclerosis in Clock^Δ19/Δ19apolipoprotein E (ApoE)^-/- mice. These findings point to a mechanism whereby CLOCK exerts a protective effect against EndMT and atherosclerotic plaque accumulation.

METHODS

Cultured human umbilical vein endothelial cells (HUVECs) were stimulated with 66 mM glucose for 120 h to induce EndMT. The expression of CLOCK and ROCK1 was assayed, as were their effects on EndMT. We also conducted molecular and morphometric examination of carotid artery plaques from patients with carotid artery stenosis to assess the clinical relevance of these findings.

RESULTS

Upon EndMT, HUVECs exhibited decreased CLOCK expression and increased ROCK1 expression. Notably, CLOCK silencing increased high glucose-induced EndMT, migration ability, and ROCK1 activation, while overexpressing CLOCK attenuated these characteristics. Moreover, inhibition of ROCK1 largely blocked EndMT induced by high-glucose or transforming growth factor (TGF)-β1 but failed to rescue the reduced CLOCK expression. The vulnerability of human carotid artery plaque was strongly correlated with loss of CLOCK expression, activation of TGF-β/ROCK1 signaling, and the extent of EndMT.

CONCLUSIONS

The data indicate that loss of protective endothelial CLOCK expression aggravates TGF-β/ROCK1-modulated EndMT progression, which contributes to the vulnerability of human carotid plaque.

The incretin hormone GIP is upregulated in patients with atherosclerosis and stabilizes plaques in ApoE-/- mice by blocking monocyte/macrophage activation

OBJECTIVE

The incretin hormones GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic peptide) are secreted by the gut after food intake leading to pancreatic insulin secretion and glucose lowering. Beyond its role in glucose control, GLP-1 was found in mice and men to beneficially modulate the process of atherosclerosis, which has been linked to improved cardiovascular outcome of patients with diabetes at high cardiovascular risk treated with GLP-1 receptor agonists. However, little is known on the role of the other main incretin in the cardiovascular system. The aim of this study was to characterize GIP in atherosclerotic cardiovascular disease.

METHODS AND RESULTS

Serum concentrations of GIP were assessed in 731 patients who presented for elective coronary angiography at the University Hospital Aachen. While GIP concentrations were not associated with coronary artery disease (CAD), we found 97 patients with PAD (peripheral artery disease) vs. 634 without PAD to have higher circulating GIP levels (413.0 ± 315.3 vs. 332.7 ± 292.5 pg/mL, p = 0.0165). GIP levels were independently related to PAD after multivariable adjustment for CAD, age, sex, BMI, hypertension, diabetes, CRP, WBC, and smoking. To investigate the functional relevance of elevated GIP levels in human atherosclerotic disease, we overexpressed GIP (1-42) in ApoE^-/- mice fed a Western diet for 12 weeks using an adeno-associated viral vector system. GIP overexpression led to reduced atherosclerotic plaque macrophage infiltration and increased collagen content compared to control (LacZ) with no change in overall lesion size, suggesting improved plaque stability. Mechanistically, we found GIP treatment to reduce MCP-1-induced monocyte migration under In vitro conditions. Additionally, GIP prevented proinflammatory macrophage activation leading to reduced LPS-induced IL-6 secretion and inhibition of MMP-9 activity, which was attributable to GIP dependent inhibition of NfκB, JNK-, ERK, and p38 in endotoxin activated macrophages.

CONCLUSION

Elevated concentrations of the incretin hormone GIP are found in patients with atherosclerotic cardiovascular disease, while GIP treatment attenuates atherosclerotic plaque inflammation in mice and abrogates inflammatory macrophage activation in vitro. These observations identified GIP as a counterregulatory vasoprotective peptide, which might open new therapeutic avenues for the treatment of patients with high cardiovascular risk.

Standardized fraction of Xylocarpus moluccensis fruits improve vascular relaxation and plaque stability in dyslipidemic models of atherosclerosis

ETHNOPHARMACOLOGICAL RELEVANCE

Xylocarpus moluccensis (Lamk.) M. Roem of family Meliaceae has triterpenoids rich fruits. Triterpenoids have been known to possess cardioprotection and anti-atherosclerotic activities (Han and Bakovic, 2015; Wu et al., 2009). Standardized fraction of these fruits exhibited anti-dyslipidemic (Srivastava et al., 2015), anti-inflammatory (Ravangpai et al., 2011) and CNS depressant activity (Sarker et al., 2007). However, there is no report in the literature on its cardiovascular effects.

AIM OF THE STUDY

The present study was undertaken to assess vasoprotective, anti-atherosclerotic and further examine the anti-dyslipidemic effect of the standardized fraction of Xylocarpus moluccensis (F018) fruits in the mechanical injury and high fat diet (HFD) induced dyslipidemic/ atherosclerosis models.

MATERIALS AND METHODS

Guinea pigs were fed 0.08% cholesterol + 15% fat diet for 3 weeks, while ApoE KO mice were fed high fat diet for 18 weeks to induce dyslipidemia and atherosclerosis. A combination of balloon injury and high fat diet (1% cholesterol, 6% peanut oil) for 5 weeks was used to accelerate atherosclerosis in NZW rabbits. F018 was administered once daily by oral route in guinea pigs (10, 25 or 50mg/kg/day for 3 weeks), ApoE KO mice (50mg/kg/day for 6 weeks) and in NZW rabbit (25mg/kg/day for 5 weeks) to monitor its effect on dyslipidemia, vasoreactivity and plaque composition by using standard methodologies.

RESULTS

F018 treatment in guinea pigs (25 and 50mg/kg/day), ApoE mice (50mg/kg/day) and rabbits (25mg/kg/day) significantly reduced plasma lipids and improved ACh induced vasorelaxation. Anti-dyslipidemic effect of F018 seems to be due to the modulation of enterohepatic genes involved in the cholesterol absorption and excretion. Moreover, significant improvement in the acetylcholine (ACh) induced vasorelaxation was accompanied with reduced inflammatory burden and enhanced activation of eNOS in ApoE mice aortic tissue. Similarly inflammatory cytokines, immunolabeling of macrophage marker (CD68) and MMP-9 were reduced along with augmentation in vascular smooth muscle cells and collagen type I and III in the mechanically injured iliac artery segment in the rabbits.

CONCLUSIONS

Altogether, F018 preserved vasoreactivity, reduced atherosclerotic plaque progression and enhanced plaque stability by reducing lipids, inflammatory cytokines, improving endothelial function and collagen content.

Bromodomain-containing protein 7 deficiency augments atherosclerotic lesions in ApoE-/- mice

Atherosclerotic plaque formation is characterized by the persistence of lipid-laden macrophages on the inner walls of arteries. Chronic inflammation and imbalanced macrophage function are likely to play a critical role. Herein, we investigated whether bromodomain-containing protein 7 (Brd7), a member of the bromodomain-containing protein family, regulates atherosclerosis, and if so, which mechanisms are responsible for the process. We found that Brd7 is expressed in mouse atherosclerotic plaques, and mostly in macrophages. Inhibition of Brd7 accelerates atherosclerotic lesion formation in ApoE^-/- mice by promoting NF-κB-mediated inflammation. Furthermore, Brd7 inhibition alters the phenotype of macrophages and promotes plaque instability, at least partly via STAT6 signaling. Our data define a previously undescribed role of Brd7 in the development of atherosclerosis.

AG1296 enhances plaque stability via inhibiting inflammatory responses and decreasing MMP-2 and MMP-9 expression in ApoE-/- mice

BACKGROUND

Atherosclerosis is a chronic process that progresses to unstable plaques. Plaque rupture leads to deleterious consequences such as acute coronary syndrome, thrombosis and stroke. AG1296 is a potent tyrosine kinase inhibitor which is able to block PDGF-PDGFR signaling pathway. This study aims to assess the effect of AG1296 on plaque stability and explore the potential mechanisms.

METHODS

Atherosclerotic plaques were induced in carotid arteries in ApoE-/- mice by perivascular collar placement. All mice were randomly divided into PBS and AG1296 groups. 3 weeks after the surgery, the carotid arteries were harvested for histological analysis.

RESULTS

In AG1296 group, plaque area decreased by 41.5% (p = 0.0041) and the contents of macrophages and lipids decreased by 43.5% (p = 0.0003) and 35.6% (p = 0.0032) respectively. The contents of smooth muscle cells increased by 22.3% (p = 0.0214) in AG1296 group. Vulnerable index decreased by 48.3% (p = 0.0002). The inflammation factors IL-6 and TNF- alpha decreased by 49.0% (p = 0.0008) and 51.8% (p < 0.0001) and matrix metalloproteinases MMP-2 and MMP-9 decreased by 54.1% (p = 0.0004) and 37.1% (p < 0.0001) in AG1296 group. M1 macrophage markers (MCP-1) were downregulated by 30.3% (p = 0.0007) and M2 macrophage markers (ARG-1) were increased by 55.2% (p = 0.0009) in AG1296 group.

CONCLUSION

AG1296 inhibited the atherosclerotic plaque progression and enhanced plaque stability by inhibiting inflammatory responses, reducing the expression of matrix metalloproteinases and promoting macrophages from proinflammatory phenotype to anti-inflammatory phenotype.

Incretin treatment and atherosclerotic plaque stability: Role of adiponectin/APPL1 signaling pathway

AIMS

Glucagon like peptide 1 (GLP-1) analogues and dipeptidyl peptidase IV (DPP-4) inhibitors reduce atherosclerosis progression in type 2 diabetes mellitus (T2DM) patients and are associated with morphological and compositional characteristics of stable plaque phenotype. GLP-1 promotes the secretion of adiponectin which exerts anti-inflammatory effects through the adaptor protein PH domain and leucine zipper containing 1 (APPL1). The potential role of APPL1 expression in the evolution of atherosclerotic plaque in TDM2 patients has not previously evaluated.

METHODS

The effect of incretin therapy in the regulation of adiponectin/APPL1 signaling was evaluated both on carotid plaques of asymptomatic diabetic (n=71) and non-diabetic patients (n=52), and through in vitro experiments on endothelial cell (EC).

RESULTS

Atherosclerotic plaques of T2DM patients showed lower adiponectin and APPL1 levels compared with non-diabetic patients, along with higher oxidative stress, tumor necrosis factor-α (TNF-α), vimentin, and matrix metalloproteinase-9 (MMP-9) levels. Among T2DM subjects, current incretin-users presented higher APPL1 and adiponectin content compared with never incretin-users. Similarly, in vitro observations on endothelial cells co-treated with high-glucose (25mM) and GLP-1 (100nM) showed a greater APPL1 protein expression compared with high-glucose treatment alone.

CONCLUSIONS

Our findings suggest a potential role of adiponectin/APPL1 signaling in mediating the effect of incretin in the prevention of atherosclerosis progression or plaque vulnerability in T2DM.

The Roles of CD137 Signaling in Atherosclerosis

The tumor necrosis factor receptor superfamily (TNFRSF), which includes CD40, LIGHT, and OX40, plays important roles in the initiation and progression of cardiovascular diseases, involving atherosclerosis. CD137, a member of TNFRSF, is a well-known activation-induced T cell co-stimulatory molecule and has been reported to be expressed in human atherosclerotic plaque lesions, and plays pivotal roles in mediating disease processes. In this review, we focus on and summarize recent advances in mouse studies on the involvement of CD137 signaling in the pathogenesis and plaque stability of atherosclerosis, thereby highlighting a valuable therapeutic target in atherosclerosis.

Mast cells are increased in the media of coronary lesions in patients with myocardial infarction and may favor atherosclerotic plaque instability

OBJECTIVES

Mast cells (MCs) may play an important role in plaque destabilization and atherosclerotic coronary complications. Here, we have studied the presence of MCs in the intima and media of unstable and stable coronary lesions at different time points after myocardial infarction (MI).

METHODS

Coronary arteries were obtained at autopsy from patients with acute MI (up to 5 days old; n=27) and with chronic MI (5-14 days old; n=18), as well as sections from controls without cardiac disease (n=10). Herein, tryptase-positive MCs were quantified in the intima and media of both unstable and stable atherosclerotic plaques in infarct-related and non-infarct-related coronary arteries.

RESULTS

In the media of both acute and chronic MI patients, the number of MCs was significantly higher than in controls. This was also found when evaluating unstable and stable plaques separately. In patients with chronic MI, the number of MCs in unstable lesions was significantly higher than in stable lesions. This coincided with a significant increase in the relative number of unstable plaques in patients with chronic MI compared with control and acute MI. No differences in MC density were found between infarct-related and non-infarct-related coronary arteries in patients with MI.

CONCLUSION

The presence of MCs in the media of both stable and unstable atherosclerotic coronary lesions after MI suggests that MCs may be involved in the onset of MI and, on the other hand, that MI triggers intra-plaque infiltration of MCs especially in unstable plaques, possibly increasing the risk of re-infarction.

TRAF3IP2 mediates atherosclerotic plaque development and vulnerability in ApoE(-/-) mice

BACKGROUND AND AIMS

Atherosclerosis is a major cause of heart attack and stroke. Inflammation plays a critical role in the development of atherosclerosis. Since the cytoplasmic adaptor molecule TRAF3IP2 (TRAF3-Interacting Protein 2) plays a causal role in various autoimmune and inflammatory diseases, we hypothesized that TRAF3IP2 mediates atherosclerotic plaque development.

METHODS

TRAF3IP2/ApoE double knockout (DKO) mice were generated by crossing TRAF3IP2(-/-) and ApoE(-/-) mice. ApoE(-/-) mice served as controls. Both DKO and control mice were fed a high-fat diet for 12 weeks. Plasma lipids were measured by ELISA, atherosclerosis by en face analysis of aorta and plaque cross-section measurements at the aortic valve region, plaque necrotic core area, collagen and smooth muscle cell (SMC) content by histomorphometry, and aortic gene expression by RT-qPCR.

RESULTS

The plasma lipoprotein profile was not altered by TRAF3IP2 gene deletion in ApoE(-/-) mice. While total aortic plaque area was decreased in DKO female, but not male mice, the plaque necrotic area was significantly decreased in DKO mice of both genders. Plaque collagen and SMC contents were increased significantly in both female and male DKO mice compared to respective controls. Aortic expression of proinflammatory cytokine (Tumor necrosis factor α, TNFα), chemokine (Chemokine (C-X-C motif) Ligand 1, CXCL1) and adhesion molecule (Vascular cell adhesion molecule 1, VCAM1; and Intercellular adhesion molecule 1, ICAM1) gene expression were decreased in both male and female DKO mice. In addition, the male DKO mice expressed markedly reduced levels of extracellular matrix (ECM)-related genes, including TIMP1 (Tissue inhibitor of metalloproteinase 1), RECK (Reversion-Inducing-Cysteine-Rich Protein with Kazal Motifs) and ADAM17 (A Disintegrin And Metalloproteinase 17).

CONCLUSIONS

TRAF3IP2 plays a causal role in atherosclerotic plaque development and vulnerability, possibly by inducing the expression of multiple proinflammatory mediators. TRAF3IP2 could be a potential therapeutic target in atherosclerotic vascular diseases.

The role of macrophage transcription factor MafB in atherosclerotic plaque stability

BACKGROUND AND AIMS

Macrophage differentiation is associated with the development of atherosclerosis and plaque vulnerability and is regulated by transcription factor MafB. We previously reported that MafB attenuates macrophage apoptosis, which is associated with atherosclerotic plaque instability. The aim of this study was to elucidate the role of MafB in the progression of atherosclerotic plaque.

METHODS

We generated macrophage-specific dominant-negative (DN) MafB transgenic mice and intercrossed DN-MafB mice with apolipoprotein E (ApoE) knockout (KO) mice.

RESULTS

There was no significant difference in advanced atherosclerotic lesion area between DN-MafB/ApoE KO mice and littermate control ApoE KO mice 9 weeks after high-cholesterol diet. However, DN-MafB/ApoE KO mice showed significantly larger necrotic cores and lower collagen content in atherosclerotic plaques than ApoE KO mice. Although there was no difference in intraplaque macrophage infiltration and efferocytosis, DN-MafB/ApoE KO mice showed significantly more apoptotic macrophages at the plaque edges than did ApoE KO mice. Real-time PCR analysis revealed that peritoneal macrophages of DN-MafB/ApoE KO mice had a greater increase in matrix metalloproteinase-9 and mRNA expression of inflammatory/M1 macrophage markers (tissue necrosis factor-α, interleukin-6, CD11c, and p47phox) after lipopolysaccharide stimulation than those of ApoE KO mice.

CONCLUSION

Macrophage-specific inhibition of MafB may destabilize atherosclerotic plaques in advanced lesions.

Preventive and therapeutic moderate aerobic exercise programs convert atherosclerotic plaques into a more stable phenotype

The mechanisms by which exercise affects atherosclerotic plaque stability remain incompletely understood. We evaluated the effects of two training protocols on both atherosclerotic plaque structure and the signaling pathways involved in plaque rupture.

METHODS

Male low-density lipoprotein (LDL) receptor knockout mice were fed a high-fat, high-cholesterol diet (HFD). One group was subjected to moderate exercise using a treadmill for 14weeks (preventive protocol). The other group started an exercise regimen after 16weeks of the HFD (therapeutic group). Atherosclerotic plaques within the aorta were evaluated for lipid and collagen contents, as well as for inflammatory markers. Plasma cholesterol and cytokine levels were also determined.

RESULTS

The mice receiving a HFD developed hypercholesterolemia and atherosclerotic plaques within the aorta. The aortas from the animals in the preventive protocol exhibited smaller lipid cores and higher collagen content. These animals also exhibited lower CD40 expression within the plaques. The aortas of the mice in the therapeutic group exhibited higher collagen content, but no differences in either lipid core size or plaque size were noted. No differences in blood pressure, plasma cholesterol, cytokine levels, plaque size or metalloproteinase 9 expression were observed in the trained animals compared with the sedentary animals.

CONCLUSION

Moderate aerobic exercise modified atherosclerotic plaque characteristics and converted the plaques into a more stable phenotype, increasing the collagen content in response to both exercise programs. Furthermore, moderate aerobic exercise reduced the animals' fat content and decreased the activity of the CD40-CD40L signaling pathway in the preventive group.

Insulin inhibits inflammation and promotes atherosclerotic plaque stability via PI3K-Akt pathway activation

Toll-like receptor (TLR) 4 induced inflammation was reported to play an important role in atherosclerotic plaque stability. Recent studies indicated that insulin could inhibit inflammation by activating phosphatidylinositol 3-kinase-Akt-dependent (PI3K-Akt) signaling pathway. In the current study, we hypothesized that insulin would inhibit TLR4 induced inflammation via promoting PI3K-Akt activation, thus enhancing the stabilization of atherosclerotic plaques. In order to mimic the process of plaque formation, monocyte-macrophage lineage RAW264.7 were cultured and induced to form foam cells by oxidized LDL (ox-LDL). Oil red O staining results showed that insulin significantly restrained ox-LDL-induced foam cell formation. Analysis of inflammatory reaction during foam cell formation indicated that insulin significantly down-regulated the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-6 levels, inhibited TLR4, myeloid differentiation primary response gene (MyD) 88 and nuclear factor (NF)-κB. Further mechanism analysis showed that pretreating with the PI3K blocker, wortmannin dramatically dampened the insulin-induced up-regulation of pAkt expression. Additionally, blockade of PI3K-Akt signaling also dampened the immunosuppression effect brought by insulin. Following the construction of a rodent atherosclerosis model, pretreatment of insulin resulted in an evident decrease in lipid deposition of the blood vessel wall, serum levels of TNF-α and IL-6, and numbers of infiltrated macrophages and foam cells. Taken together, these results suggested that insulin might inhibit inflammation and promote atherosclerotic plaque stability via the PI3K-Akt pathway by targeting TLR4-MyD88-NF-κB signaling. Our findings may provide a potential target for the prevention of cardiovascular disease.

Shear stress-induced atherosclerotic plaque composition in ApoE(-/-) mice is modulated by connexin37

OBJECTIVE

Shear stress patterns influence atherogenesis and plaque stability; low laminar shear stress (LLSS) promotes unstable plaques whereas oscillatory shear stress (OSS) induces more stable plaques. Endothelial connexin37 (Cx37) expression is also regulated by shear stress, which may contribute to localization of atherosclerotic disease. Moreover, Cx37 reduces initiation of atherosclerosis by inhibiting monocyte adhesion. The present work investigates the effect of Cx37 on the phenotype of plaques induced by LLSS or OSS.

METHODS

Shear stress-modifying casts were placed around the common carotid artery of ApoE(-/-) or ApoE(-/-)Cx37(-/-) mice, and animals were placed on a high-cholesterol diet for 6 or 9 weeks. Atherosclerotic plaque size and composition were assessed by immunohistochemistry.

RESULTS

Plaque size in response to OSS was increased in ApoE(-/-)Cx37(-/-) mice compared to ApoE(-/-) animals. Most plaques contained high lipid and macrophage content and a low amount of collagen. In ApoE(-/-) mice, macrophages were more prominent in LLSS than OSS plaques. This difference was reversed in ApoE(-/-)Cx37(-/-) animals, with a predominance of macrophages in OSS plaques. The increase in macrophage content in ApoE(-/-)Cx37(-/-) OSS plaques was mainly due to increased accumulation of M1 and Mox macrophage subtypes. Cx37 expression in macrophages did not affect their proliferation or their polarization in vitro.

CONCLUSION

Cx37 deletion increased the size of atherosclerotic lesions in OSS regions and abrogated the development of a stable plaque phenotype under OSS in ApoE(-/-) mice. Hence, local hemodynamic factors may modify the risk for adverse atherosclerotic disease outcomes associated to a polymorphism in the human Cx37 gene.

Molecular hydrogen stabilizes atherosclerotic plaque in low-density lipoprotein receptor-knockout mice

Hydrogen (H(2)) attenuates the development of atherosclerosis in mouse models. We aimed to examine the effects of H(2) on atherosclerotic plaque stability. Low-density lipoprotein receptor-knockout (LDLR(-/-)) mice fed an atherogenic diet were dosed daily with H(2) and/or simvastatin. In vitro studies were carried out in an oxidized-LDL (ox-LDL)-stimulated macrophage-derived foam cell model treated with or without H(2). H(2) or simvastatin significantly enhanced plaque stability by increasing levels of collagen, as well as reducing macrophage and lipid levels in plaques. The decreased numbers of dendritic cells and increased numbers of regulatory T cells in plaques further supported the stabilizing effect of H(2) or simvastatin. Moreover, H(2) treatment decreased serum ox-LDL level and apoptosis in plaques with concomitant inhibition of endoplasmic reticulum stress (ERS) and reduction of reactive oxygen species (ROS) accumulation in the aorta. In vitro, like the ERS inhibitor 4-phenylbutyric acid, H(2) inhibited ox-LDL- or tunicamycin (an ERS inducer)-induced ERS response and cell apoptosis. In addition, like the ROS scavenger N-acetylcysteine, H(2) inhibited ox-LDL- or Cu(2+) (an ROS inducer)-induced reduction in cell viability and increase in cellular ROS. Also, H(2) increased Nrf2 (NF-E2-related factor-2, an important factor in antioxidant signaling) activation and Nrf2 small interfering RNA abolished the protective effect of H(2) on ox-LDL-induced cellular ROS production. The inhibitory effects of H(2) on the apoptosis of macrophage-derived foam cells, which take effect by suppressing the activation of the ERS pathway and by activating the Nrf2 antioxidant pathway, might lead to an improvement in atherosclerotic plaque stability.

Diminazene enhances stability of atherosclerotic plaques in ApoE-deficient mice

Angiotensin (Ang) II contributes to the development of atherosclerosis, while Ang-(1-7) has atheroprotective actions. Accordingly, angiotensin-converting enzyme 2 (ACE2), which breaks-down Ang II and forms Ang-(1-7), has been suggested as a target against atherosclerosis. Here we investigated the actions of diminazene, a recently developed ACE2 activator compound, in a model of vulnerable atherosclerotic plaque. Atherosclerotic plaque formation was induced in the carotid artery of ApoE-deficient mice by a shear stress (SS) modifier device. The animals were treated with diminazene (15mg/kg/day) or vehicle. ACE2 was strongly expressed in the aortic root and low SS-induced carotid plaques, but poorly expressed in the oscillatory SS-induced carotid plaques. Diminazene treatment did not change the lesion size, but ameliorated the composition of aortic root and low SS-induced carotid plaques by increasing collagen content and decreasing both MMP-9 expression and macrophage infiltration. Interestingly, these beneficial effects were not observed in the oscillatory SS-induced plaque. Additionally, diminazene treatment decreased intraplaque ICAM-1 and VCAM-1 expression, circulating cytokine and chemokine levels and serum triglycerides. In summary, ACE2 was distinctively expressed in atherosclerotic plaques, which depends on the local pattern of shear stress. Moreover, diminazene treatment enhances the stability of atherosclerotic plaques.

Angiopoietin-2 blocking antibodies reduce early atherosclerotic plaque development in mice

OBJECTIVE

Angiopoietin-2 (Ang-2) blocking agents are currently undergoing clinical trials for use in cancer treatment. Ang-2 has also been associated with rupture-prone atherosclerotic plaques in humans, suggesting a role for Ang-2 in plaque stability. Despite the availability of Ang-2 blocking agents, their clinical use is still lacking. Our aim was to establish if Ang-2 has a role in atheroma development and in the transition of subclinical to clinically relevant atherosclerosis. We investigated the effect of antibody-mediated Ang-2 blockage on atherogenesis after in a mouse model of atherosclerosis.

METHODS

Hypercholesterolemic (low-density lipoprotein receptor(-/-) apolipoprotein B(100/100)) mice were subjected to high-cholesterol diet for eight weeks, one group with and one group without Ang-2 blocking antibody treatment during weeks 4-8.To enhance plaque development, a peri-adventitial collar was placed around the carotid arteries at the start of antibody treatment. Aortic root, carotid arteries and brachiocephalic arteries were analyzed to evaluate the effect of Ang-2 blockage on atherosclerotic plaque size and stable plaque characteristics.

RESULTS

Anti-Ang-2 treatment reduced the size of fatty streaks in the brachiocephalic artery (-72%, p < 0.05). In addition, antibody-mediated Ang-2 blockage reduced plasma triglycerides (-27%, p < 0.05). In contrast, Ang-2 blockage did not have any effect on the size or composition (collagen content, macrophage percentage, adventitial microvessel density) of pre-existing plaques in the aortic root or collar-induced plaques in the carotid artery.

CONCLUSIONS

Ang-2 blockage was beneficial as it decreased fatty streak formation and plasma triglyceride levels, but had no adverse effect on pre-existing atherosclerosis in hypercholesterolemic mice.

Clinical significance of macrophage phenotypes in cardiovascular disease

The emerging understanding of macrophage subsets and their functions in the atherosclerotic plaque has led to the consensus that M1 macrophages are pro-atherogenic while M2 macrophages may promote plaque stability, primarily though their tissue repair and anti-inflammatory properties. As such, modulating macrophage function to promote plaque stability is an exciting therapeutic prospect. This review will outline the involvement of the different macrophage subsets throughout atherosclerosis progression and in models of regression. It is evident that much of our understanding of macrophage function comes from in vitro or small animal models and, while such knowledge is valuable, we have much to learn about the roles of the macrophage subsets in the clinical setting in order to identify the key pathways to target to possibly promote plaque stability.

RETRACTED: Probucol via inhibition of NHE1 attenuates LPS-accelerated atherosclerosis and promotes plaque stability in vivo

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the authors. Concern had previously been raised about the veracity of some of the data in Figure 6 which appears to contain similar experimental data to many other publications, described here: https://pubpeer.com/publications/72ACDBE9751C8FD443A223FEB806E8#. The corresponding author contacted the journal and acknowledged that some of the experiments were not conducted by the authors themselves and they no longer have confidence in the reliability of the results. The authors would like to apologize for any inconvenience caused. The Editor-in-Chief agreed to retract the article.

Clinical pharmacology of n-3 polyunsaturated fatty acids: non-lipidic metabolic and hemodynamic effects in human patients

A high dietary intake of n-3 long chain polyunsaturated fatty acids (PUFA), eicosapentaenoic and docosahexaenoic acids, is associated with a reduced incidence of coronary events. Supplementation with pharmacological doses of the same may improve survival in patients with previous myocardial infarction and established heart failure. Such protective effects may be explained by the action of n-3 PUFA on systemic inflammation, hypertension, endothelial dysfunction, thrombosis, cardiac arrhythmias, heart rate variability and atherosclerotic plaque instability, which are involved in the pathogenesis of these clinical conditions. In this short paper we will review the evidence in support of these pleiotropic effects of n-3 fatty acids.